igneous
Basalt Pebble
Extrusive igneous rock
Hardness: 6 on the Mohs scale; Color: Dark grey to black; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained), microscopic crystals.
- Hardness
- 6 on the Mohs scale
- Color
- Dark grey to black
- Luster
- Dull to sub-vitreous
Identified More igneous →
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Physical properties
Hardness: 6 on the Mohs scale; Color: Dark grey to black; Luster: Dull to sub-vitreous; Crystal structure: Aphanitic (fine-grained), microscopic crystals.
Formation & geological history
Formed from the rapid cooling of low-viscosity lava rich in iron and magnesium exposed at or very near the Earth's surface, typically over millions of years.
Uses & applications
Commonly used in construction, as aggregate in concrete, road base, and occasionally in landscaping or stone polishing.
Geological facts
Basalt is the most common rock type in the Earth's crust underlying the ocean basins and is also found abundantly on the Moon and Mars.
Field identification & locations
Found in riverbeds, beaches, and glacial till worldwide as water-worn pebbles. Identified by its fine grain, heavy feel, and dark coloration.
